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//
// Implementation of inline methods of G4TwistTrapAlphaSide.
// --------------------------------------------------------------------

inline
G4double G4TwistTrapAlphaSide::GetValueA(G4double phi)
{
  return ( fDx4plus2 + fDx4minus2 * ( 2 * phi ) / fPhiTwist  ) ;
}

inline
G4double G4TwistTrapAlphaSide::GetValueD(G4double phi) 
{
  return ( fDx3plus1 + fDx3minus1 * ( 2 * phi) / fPhiTwist  ) ;
} 

inline 
G4double G4TwistTrapAlphaSide::GetValueB(G4double phi) 
{
  return ( fDy2plus1 + fDy2minus1 * ( 2 * phi ) / fPhiTwist ) ;
}


inline
G4double G4TwistTrapAlphaSide::Xcoef(G4double u, G4double phi)
{
  
  return GetValueA(phi)/2. + (GetValueD(phi)-GetValueA(phi))/4. 
    - u*( ( GetValueD(phi)-GetValueA(phi) )/( 2 * GetValueB(phi) ) - fTAlph );

}

inline G4ThreeVector
G4TwistTrapAlphaSide::SurfacePoint(G4double phi, G4double u , G4bool isGlobal)
{
  // function to calculate a point on the surface, given by parameters phi,u

  G4ThreeVector SurfPoint ( Xcoef(u,phi) * std::cos(phi)
                          - u * std::sin(phi) + fdeltaX*phi/fPhiTwist,
                            Xcoef(u,phi) * std::sin(phi)
                          + u * std::cos(phi) + fdeltaY*phi/fPhiTwist,
                            2*fDz*phi/fPhiTwist  );
  if (isGlobal) { return (fRot * SurfPoint + fTrans); }
  return SurfPoint;
}

inline
G4double G4TwistTrapAlphaSide::GetBoundaryMin(G4double phi)
{
  return -0.5*GetValueB(phi) ;
}

inline
G4double G4TwistTrapAlphaSide::GetBoundaryMax(G4double phi)
{
  return 0.5*GetValueB(phi) ;
}

inline
G4double G4TwistTrapAlphaSide::GetSurfaceArea()
{
  return (fDz*(std::sqrt(16*fDy1*fDy1
             + (fa1md1 + 4*fDy1*fTAlph)*(fa1md1 + 4*fDy1*fTAlph))
             + std::sqrt(16*fDy2*fDy2 + (fa2md2 + 4*fDy2*fTAlph)
                                      * (fa2md2 + 4*fDy2*fTAlph))))/2. ;
}

inline
G4ThreeVector G4TwistTrapAlphaSide::NormAng( G4double phi, G4double u ) 
{
  // function to calculate the norm at a given point on the surface
  // replace a1-d1

  G4ThreeVector nvec ( fDy1* fDz*(4*fDy1*std::cos(phi)
                     + (fa1md1 + 4*fDy1*fTAlph)*std::sin(phi)),
                       -(fDy1* fDz*((fa1md1 + 4*fDy1*fTAlph)*std::cos(phi)
                     - 4*fDy1*std::sin(phi))),
                       (fDy1*(-8*(fDx3minus1 + fDx4minus2)*fDy1
                                + fa1md1*(fDx2 + fDx3plus1 + fDx4)*fPhiTwist
                                + 4*(fDx2 + fDx3plus1 + fDx4)*fDy1*fPhiTwist
                                *fTAlph + 2*(fDx3minus1 + fDx4minus2)
                                *(fa1md1 + 4*fDy1*fTAlph)*phi)
                                + fPhiTwist*(16*fDy1*fDy1
                                + (fa1md1 + 4*fDy1*fTAlph)
                                *(fa1md1 + 4*fDy1*fTAlph))*u
                                + 4*fDy1*(fa1md1*fdeltaY - 4*fdeltaX*fDy1
                                + 4*fdeltaY*fDy1*fTAlph)* std::cos(phi)
                                - 4*fDy1*(fa1md1*fdeltaX + 4*fDy1*(fdeltaY
                                + fdeltaX*fTAlph))*std::sin(phi))/ 8. ) ;
  return nvec.unit();
}